We propose a novel wavefront sensor for radio telescopes with a point diffraction interferometer. A point-like object is set at a pupil plane and the electric field at the focal plane is measured. A receiver dedicated to the novel sensor is prepared which has delay lines to make interferograms. A procedure to estimate the electric field at the pupil is shown analytically. Numerical simulation reveals that the proposed system allows us to measure the phase of the electric field at the pupil with a precision of about &lambda;/28.

LiteBIRD is a next generation satellite aiming for the detection of the Cosmic Microwave Background (CMB) B-mode polarization imprinted by the primordial gravitational waves generated in the era of the inflationary universe. The science goal of LiteBIRD is to measure the tensor-to-scaler ratio r with a precision of &delta;r &lt; 10<sup>-3</sup>&diams;, oﬀering us a crucial test of the major large-single-field slow-roll inflation models. LiteBIRD is planned to conduct an all sky survey at the sun-earth second Lagrange point (L2) with an angular resolution of about 0.5 degrees to cover the multipole moment range of 2 &le; &ell; &le; 200. We use focal plane detector arrays consisting of 2276 superconducting detectors to measure the frequency range from 40 to 400 GHz with the sensitivity of
3.2 &mu;K·arcmin. including the ongoing studies.

Polarized patterns in the cosmic microwave background (CMB) radiation contains rich knowledge for early stage of the universe. In particular their odd-parity patterns at large angular scale (&gt; 1&deg;), primordial B-modes, are smoking-gun evidence for the cosmic inflation. The GroundBIRD experiment aims to detect these B-modes with a ground-based apparatus that includes several novel devices: a high-speed rotational scan system, cold optics, and microwave kinetic inductance detectors (MKIDs). We plan to start observations in the Canary Islands in 2017. In this paper, we present the status of the development of our instruments. We established an environment that allows operation of our MKIDs in an optical configuration, in which the MKIDs observe radiations from the outside of the telescope aperture. We have also constructed MKID prototypes, and we are testing them in the optical configuration.

We present the mission design of LiteBIRD, a next generation satellite for the study of B-mode polarization and inflation from cosmic microwave background radiation (CMB) detection. The science goal of LiteBIRD is to measure the CMB polarization with the sensitivity of &delta;r = 0:001, and this allows testing the major single-field slow-roll inflation models experimentally. The LiteBIRD instrumental design is purely driven to achieve this goal. At the earlier stage of the mission design, several key instrumental specifications, e.g. observing band, optical system, scan strategy, and orbit, need to be defined in order to process the rest of the detailed design. We have gone through the feasibility studies for these items in order to understand the tradeoffs between the requirements from the science goal and the compatibilities with a satellite bus system. We describe the overview of LiteBIRD and discuss the tradeoffs among the choices of scientific instrumental specifications and strategies. The first round of feasibility studies will be completed by the end of year 2014 to be ready for the mission definition review and the target launch date is in early 2020s.

We have developed a 30-cm submillimeter-wave telescope intended to survey the Milky Way in 500 GHz emission lines at the Dome Fuji station in Antarctic plateau. Transportability and low power consumption are required while keeping low system noise temperature for the operation in Antarctica. The telescope is designed to be divided into five components and to operate with less than 2.5 kW of electric power. Its receiver noise temperature is less than 85 K in SSB at 461 and 492 GHz. We succeeded in operating the telescope at -30◦C in laboratory that is a typical temperature of the Dome Fuji in summer.

Polarimeters used in cosmic microwave background (CMB) experiments must be well calibrated to measure
faint CMB polarization patterns with low systematic errors. Polarimeter characteristics generally vary with
the incident load temperature (<i>T</i><sub>load</sub>). Therefore, re-producing the observing conditions in the laboratory is an
important concern. For polarimeters, we developed a characterization system with cryogenically cooled loads.
The loads generate unpolarized radiation (15 K and 30 K), comparable to the typical sky temperature of the
best sites on the ground, e.g., the Atacama Desert in Chile (<i>T</i><sub>load</sub> ∼ 15 K). The radiation from the loads is
reflected by a metal mirror in the cryostat, yielding partially polarized radiation (600 mK), entering a feed horn
on the polarimeter. Rotation of the mirror alters the incident angle of the polarization and causes periodic
switching of the load temperature for<i> Y</i> -factor measurements. We demonstrated the validity of the system using
a polarimeter developed for an upgrade of QUIET (QUIET-II), which can obtain the Stokes parameters <i>I, Q,</i>
and <i>U</i> simultaneously. The system characterized all the necessary properties, e.g., the responses for <i>I, Q</i>, and
<i>U,</i> and their crosstalk. In addition, a wide range of polarimeter bias conditions was surveyed. The principle of
the characterization system is not limited to a particular frequency or detection scheme. Thus, various types of
state-of-the-art detectors can be calibrated by using this system.

LiteBIRD [Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background
Radiation Detection] is a small satellite to map the polarization of the cosmic microwave background (CMB)
radiation over the full sky at large angular scales with unprecedented precision. Cosmological inflation, which
is the leading hypothesis to resolve the problems in the Big Bang theory, predicts that primordial gravitational
waves were created during the inflationary era. Measurements of polarization of the CMB radiation are known as
the best probe to detect the primordial gravitational waves. The LiteBIRD working group is authorized by the
Japanese Steering Committee for Space Science (SCSS) and is supported by JAXA. It has more than 50 members
from Japan, USA and Canada. The scientific objective of LiteBIRD is to test all the representative inflation models that satisfy single-field slow-roll conditions and lie in the large-field regime. To this end, the requirement
on the precision of the tensor-to-scalar ratio, r, at LiteBIRD is equal to or less than 0.001. Our baseline design
adopts an array of multi-chroic superconducting polarimeters that are read out with high multiplexing factors in
the frequency domain for a compact focal plane. The required sensitivity of 1.8&mu;Karcmin is achieved with 2000
TES bolometers at 100mK. The cryogenic system is based on the Stirling/JT technology developed for SPICA,
and the continuous ADR system shares the design with future X-ray satellites.

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